Alkylation of isoparaffins with ethylene



Patented Mar. 3, 1942 amm'nonor rsoraaarrms wrrn- William E. Bradley, Los Angeles, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California No Drawing. Application May z, 1938, Serial No. 205,533

i4 Claims. (Cl. 196-10) The present invention relates to the synthesis of hydrocarbons, and more particularly refers to the manufacture of paraflinic hydrocarbons of a branched chain type especially-suitable as'fuel in automobile and aviation engines.

Recently, it has been proposed to produce branched chain hydrocarbon fractions boiling within the gasoline range and having high antidetonating characteristics, by alkylating isoparafdnic hydrocarbons with olefins. This alkylation reaction was found to occur when the two hydrocarbon fractions were brought into'contact with each other in the presence of a catalyzing agent, such as sulfuric acid.

The reaction between one or more olefin molecules and one or more isoparafilnc hydrocarbon molecules produced a branched chain parafiinic molecule. This reaction is called alkylation, and the product is herein termed an alkymer in order to distinguishit from a polymer which is the product resulting from the interaction of two or more lefln molecules.

Theoretica y, the interaction between an isoparafiinic hydrocarbon and an olefinic hydrocarbon in the presence of a suitable alkylating catalyst is of a simple character. Thus, the combiwhich would satisfy the lower boiling bracket of the gasoline, it is necessary to alkylate isobutane nation which takes place when isobutane is chemically combined with a butene may be expressed by the following equation:

isobutane butene octane The above equation shows a reaction in which contain different hydrocarbons having different boiling ranges, in fact, motor fuel specifications require the presence of these various-hydrocarbons. Thus, the motor fuel fractions must have a relatively low initial boiling point for certain percentages boiling at difierent temperatures. Generally speaking, these motor fuels contain hydrocarbons ranging from the five-carbon molecules to and including the ten-carbon molecules.

Therefore, to produce a motor fuel fraction of isoparafflns with olefins it is necessary to alkylate several of the relatively low boiling-isoparaflinic hydrocarbons with difi'erent olefins. In view of the fact that the lowest isoparamn is isobutane,

"and in order to produce an alkylated fraction with ethylene, thi alkylation resulting in a fraction of isohexanes.

The'ordinary known alkylating catalysts, however, are substantially ineffectual in causing the alkylation of isoparafilns with ethylene. under ordinary conditions of operation, namely at normal temperatures and at pressures sufllcient to cause the maintenance of the hydrocarbons in a liquid phase, strong sulfuric acid will cause an eflicient combining of isoparaflins, such as isobutane and isopentane, with the normally gaseous olefins of the class of propylene, butylene and pentenes, the products of, reaction compris-" ing branched chain saturated hydrocarbons boiling within the gasoline range, having high antidetonating characteristics, and being susbtantially free from polymers boiling within this range. However, the treatment of the above isoparaflins with ethylene, under the same conditions and in the presence of the same catalyst, did not cause the combining of the isoparaflins with ethylene. It is, therefore, the main object of the present invention to provide a catalytic process which will cause the alkylation of the relatively low boiling isoparaillns with ethylene. It is a further object of this invention to provide a process which will utilize ethylene in the production of motor fuel fractions and constituents thereof, which' possess high anti-detonating characteristic's. It is a further object of the invention to provide a process wherein alkylation of isoparafiins of the class of isobutane, isopentane, and-isohexane with ethylene will be favored in preference to any polymerization of the ethylene introduced into the reaction zone for the p rpose of combining with the isoparafllnic hydrocarbons to produce alkylated fractions suitable as motor fuels or constituents thereof. It is a still further object of the invention to provide a catalyst or a catalyst mixture which is adapted to cause this alkylation of the isoparafllns with ethylene to produce the above described motor fuel fraction of the branched chain saturated type, these fractions possessing high anti-detonating qualities.

The term .isoparamns or isoparaflinic hydrocarbons, as employed in the present application and claims relates to the lower members, namely isobutane, isopentane and isohexane. The rates of alkylation of these isoparaflinic hydrocarbons, maintaining other conditions equal, are, however, not the same. Thus, the rate of alkymer formation when isopentane is employed is considerably Thus,

other hydrocarbons of the isoparaflinic class, or

as mixtures thereof with other hydrocarbons.

catalyst, this ditions the reaction may be carried out with as much as about equal quantities of sulfuric acid and of cadmium sulfate.

The ethylene used for the alkylation is introduced into the above mixture of isoparafiins and introduction being preferably gradual and accompanied by vigorous agitation.

The above and other objects may be attained A by conducting the alkylation reaction in the presence of a catalyst comprising sulfuric acid and a modifying agent of the type of a metal other salts or oxides of metals such as cadmium;

zinc, mercury, copper, silver, barium or the like.

The invention may, therefore, be stated to reside in the treatment of isoparaflinic hydrocarbons of the type of isobutane, isopentane and isohexane,'with ethylene, or with an ethylenecontaining gas, in the presence of a sulfuric acid catalyst containing one or more of the above salts and/or oxides of the enumerated metals, where by the products of reaction comprise or include alkylated branched chain 'hydrocarbonshaving a high antiknock value, said products of alkylation boiling within the gasoline range and being substantially free from polymers. The inven tion still further resides in the treatment of the relatively low-boiling isoparaflinic hydrocarbons such as isobutane, isopentane or isohexane, and mixtures thereof, with ethylene, or gases con- The preliminary commingling of the catalyst with the isoparaflins, as well as the gradual addition of the oleflns and the agitation, aid in decreasing the tendency of the ethylene to polymerize, and at the same time aid in bringing the ethylene molecules into contact with the activated isoparaflinic molecules, thereby aiding in the formation of alkymers in preference to any polymerization of the ethylene.

It is obvious that the ethylene may be impure. Thus, it may be in a gas, or in the presence of some inert gaseous materials.

The-introduction of the ethylene, or of the ethylene-containing gas, may be continued until the character of the products of reaction changes markedly. This is usually an indication that the alkylating effect of the catalyst is exhausted to taining ethylene, in the presence of a catalyst chlorides, nitrates, acetates or oxides of cadmium, zinc, mercury, copper, silver, barium or the.

like, or mixtures of these salts and/or oxides, whereby the products of reaction comprise higher boiling alkylated or branched chain hydrocarbons having high anti-detonating characteristics and suitable as fuel for use in automobile and aviation engines, said products being substantially free from polymers.

The invention still further resides in the use of relatively small percentages of the above enumerated salts and/or oxides, in combination with the sulfuric acid catalyst. Thus, although larger percentages may be employed, excellent yields are obtainable by using a sulfuric acid catalyst containing between about 1% and 10% of the above salts, as calculated on the basis of the total quan.. tity of the catalyst employed for the alkylation of the isoparaflins with ethylene. These percentages of the above salts, and particularly of the sulfates of mercury, copper, silver, zinc, cadmium or barium, when employed together with the relatively strong sulfuric acid, produce good yields of alkymers resulting from the addition of ethylene to the isoparaflins.

In operating according to the present invention, the isoparafiinic hydrocarbons, for example maintain at least the isoparaiiins in the liquidstate. The ethylene may then be conveyed into the mixture of isoparaflins and sulfuric acid catalyst containing the activating salt. ,For this purpose the pressures may be as high as 150 to 200 pounds, the reaction being realized at ordinary temperatures such as to F. It is obvious that these temperatures and pressures may be varied within a relatively wide range.

The term gasoline boiling range as employed herein refers to the average boiling range of fuels used in the ordinary automobile engines. Generally speaking, such gasoline has an initial boiling point of about F. and a maximum end point of 425 F.

In carrying out the invention, the apparatus used and the conditions of operation chosen in respect to temperature, pressure, proportions of reacting constituents, choice of strength of acid and of the metal oxide or salt, the proportions thereof, etc., may be varied to suit the individual case. The quantity of the metal salt or oxide described above may be decreased or increased with a corresponding decrease or increase inthe quantity of the acid necessary to promote the described alkylation with ethylene.

The above disclosure is merely illustrative of the preferred embodiments of tlie invention, and

isobutane, or a mixture thereof with higher mois not to be taken as limiting, since many variations thereof may be made within the scope of the following claims.

I claim:

- 1. A process of forming branched chain paraffinic hydrocarbons having high anti-detonating characteristics and suitable as motor fuel, which comprises interacting isoparaftlnic hydrocarbons having less than seven carbon atoms per molecule 2,274,858 with ethylene in the presence of a catalyst comprising strong sulfuric acid and a modifying agent selected from the class consisting of the phosphates, sulfates, chlorides, nitrates, acetates and oxides of cadmium, zinc, mercury, copper,

silver and barium.

2. In a process according to claim 1, wherein the quantity of the modifying agent comprises a relatively small percentage of the total quantity of the catalyst employed.

3. In a process according to claim 1, wherein the quantity of the modifying agent comprises between about 1% and of the total quantity of the catalyst employed.

4. A process of producing alkylated isoparaffinic hydrocarbons, boiling within the gasoline boiling range and substantially free from polymers which comprises reacting isoparafiinic hydrocarbons having less than seven carbon atoms per molecule, with ethylene in the presence of a catalyst comprising sulfuric acid of a strength between about 85% and 100% H2804 and a modifying agent adapted to cause the alkylation of the isoparaffins in preference to the polymerization of ethylene and selected from the class consisting of the phosphates, sulfates, chlorides, nitrates, acetates and oxides of cadmium, zinc, mercury, copper, silver and barium.

5. A process of forming branched chain paraffinic hydrocarbons within the gasoline boiling range, which comprises reacting low boiling isoparafiinic hydrocarbons with ethylene in the presence of a catalyst comprising sulfuric acid of a strength of about 85% to 100% H2804 and a relatively small percentage of a modifying agent selected from the class consisting of the phosphates, sulfates, chlorides, nitrates, acetates and oxides of cadmium, zinc, mercury, copper, silver and barium.

6. In a process according to claim 5, wherein the quantity of the modifying agent comprises between about 1% to 10% of the total quantityof th catalyst employed.

7. A process to produce branched chain parafflnic hydrocarbons having high anti-detonating characteristics, which comprises commingling isoparaflinic hydrocarbons having less th'an'seven carbon atoms per molecule with a catalyst consisting of strong sulfuric acid and relatively small quantities of a modifying agent selected from the class consisting of the phosphates, sulfates, chlorides, nitrates, acetates and oxides of cadmium, zinc, mercury, copper, silver and barium,

and bringing ethylene into contact with said isoparaflinic-catalyst mixture, thereby causing the alkylation of the isoparafilns with the ethylene to produce said branched chain paramns substanrange, which comprises commingling isoparafiinic hydrocarbons of less than seven carbon atoms per. molecule with a catalyst comprising sulfuric acid of a concentration between about 85% to 100% H2804 and a modifying agent selected from the class of the phosphates, sulfates, chlorides, nitrates, acetates and oxides of cadmium, zinc,

mercury, copper, silver and barium, gradually introducing an ethylene-containing gas into said isoparafiin-catalyst mixture .to cause an alkyla- 1 'tion reaction between the i-soparaiiins. and the ethylene, and separating th alkylated isoparaffins from the unreacted mixture. p

11. In a process according to claim 10, wherein the isoparafiinie hydrocarbon to be alkylated comprises isobutane, and wherein the alkylating reaction is aided by agitating the mixture.

12. A process of forming alkylated isoparaffinic hydrocarbons having high anti-detonating characteristics, which comprises commingling isoparaflinic hydrocarbons having less than seven I carbon atoms per molecule, while under pressure sufficient to maintain said hydrocarbons in a liquid state, with a catalyst comprising strong sulfuric acid and a modifying agent selected from the class consisting of the phosphates, sulfates, chlorides, nitrates, acetates and oxides'of cadmium, zinc, mercury, copper, silver'and barium, and bringing ethylene into contact with, said isoparaflin-catalyst mixture thereby causing the alkylation of isoparafiins with the ethylene to produce branched chain parafiins substantially free from products of polymerization of ethylene.

13. A process according to claim 12 wherein isobutane is employed as th'e isoparafiinic hydrocarbon fraction.

14. A process according to claim 7 wherein isobutane is employed as the isoparafiinic hydrocarbon to be alkylated and wherein the addition of the ethylene into the isobutane catalyst mixture is gradual and accompanied by vigorous agitation. f

- WILLIAM E. BRADLEY. 

